amniotic sac

(redirected from amnion NH3)
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a baglike organ or structure; see also bag, pocket, and pouch.
air s's (alveolar s's) the spaces into which the alveolar ducts open distally, and with which the alveoli communicate; see also lung.
amniotic sac the sac formed by the amnion, enclosing the fetus suspended in amniotic fluid; popularly known as the bag of waters.
conjunctival sac the potential space, lined by conjunctiva, between the eyelids and the eyeball.
endolymphatic sac the blind, flattened cerebral end of the endolymphatic duct.
hernial sac the peritoneal pouch that encloses protruding intestine.
lacrimal sac the dilated upper end of the nasolacrimal duct; see also lacrimal apparatus.
yolk sac the extraembryonic membrane connected with the midgut; in vertebrates below true mammals, it contains a yolk mass.
Yolk sac in a developing embryo. From Applegate, 2000.

amniotic sac

a thin-walled bag that contains the fetus and amniotic fluid during pregnancy. It has a capacity of 4 to 5 L at term. The wall of the sac extends from the margin of the placenta. The amnion, chorion, and decidua that make up the wall are each a few cell layers thick. They are closely applied-though not fused-to one another and to the wall of the uterus. The intact sac and its fluid provide for the equilibration of hydrostatic pressure within the uterus. During labor, the sac effects the uniform transmission of the force of uterine contractions to the cervix for dilation.

amniotic sac

An amniotic fluid-filled, thin membranous sac, which surrounds the embryo of amniote vertebrates; it provides a fluid cushion, prevents dehydration and acts as a waste receptacle during embryonic development.

amniotic sac

amnion, bag of waters, membranes Obstetrics An amniotic fluid-filled thin membraned sac which surrounds the embryo of amniote vertebrates, and provides a fluid cushion, prevents dehydration, acting as a waste receptacle during embryonic development. See Amnion.

Amniotic sac

The membranous sac that surrounds the embryo and fills with watery fluid as pregnancy advances.
Mentioned in: Childbirth


pertaining to the amnion.

amniotic fluid
the albuminous fluid contained in the amniotic sac.
amniotic plaque
small, 2 to 4 mm diameter, poxlike lesion on the inside of the amnion. Constant on the bovine amnion during the middle trimester and causes no problems nor has any known function.
amniotic sac
the amnion; the sac enclosing the fetus suspended in the amniotic fluid.
amniotic vesicle
see amniotic sac (above). Palpation of the vesicle per rectum in the cow is a common test for pregnancy between the 35th and 65th day of pregnancy.

Patient discussion about amniotic sac

Q. what does it mean when an ultrasound shows an empty amniotic sac and no baby?

A. This exact thing happened with my friend who is now 22 weeks with her first baby. She had 2 additional sacs - both empty - and the doctor said that the pregnancy had probably started out as triplets but that only one of the embryos had actually established and continued to grow.

Her doctor said it is very common for a woman to have more than one egg fertilize but that in most cases the pregnancy continues as a singleton only. She told my friend that the empty sacs would just disappear through time (which they did) and that they posed no danger to her baby.

More discussions about amniotic sac